In order to create and stabilize the aerodynamic shape of a sail, it is known to insert a batten into a pocket on the sail. The pocket generally extends from the trailing edge of the sail. The pocket is open at one end, on an edge of the sail, and the batten is forced into the pocket by means of a strap on the sail which cooperates with a friction buckle at the open end of the pocket to hold the batten in the pocket and so tension the sail along the length of the pocket. Other methods are known for securing the batten in the pocket. The batten and pocket may extend across the full width of the sail. A drawback of this system is that it results in having a strap hanging loose at the trailing edge of the sail and, to ensure adequate batten length for tensioning the sail as it stretches through use, the batten is made significantly longer than the pocket and hence projects beyond the sail edge. The protruding batten and flapping strap are unsightly and also create drag which reduces the efficiency of the sail.